Biochemical characterization and inhibitor potential of African swine fever virus thymidine kinase

African Swine Fever (ASF) is a highly contagious disease affecting both domestic pigs and wild boars. In domestic pigs, ASF is a rapidly-progressing disease with a mortality rate reaching 100 %, causing tremendous economic loss in affected areas. ASFV is caused by African Swine Fever Virus (ASFV), which is a large, enveloped double-stranded DNA virus belonging to the Asfarviridae family. ASFV has a remarkably large genome size that encodes more than 150 open reading frames. Among the virally encoded enzymes, thymidine kinase (ASFV-TK) has been shown to be critical for the efficient replication and virulence of ASFV. Here, we report the bioinformatics analysis and biochemical characterization of ASFV-TK. Amino acid sequence analysis revealed that ASFV-TK can be classified as a type II thymidine kinase. Kinetics characterization revealed a maximum velocity (V_max) and Michaelis constants (K_m) that are within the same range as previously characterized type II enzymes. ASFV-TK is competitively inhibited by the feedback inhibitor thymidine 5'-triphosphate and can use 3'-azido-3'-deoxythymidine (AZT) as a substrate with kinetics parameters comparable to those obtained with natural substrates, suggesting that nucleosides and nucleotide analogs could be explored as anti-ASFV agents.